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Zhivotovsky L.A.,Russian Academy of Sciences | Fedorova L.K.,ZAO Gidrostroy | Rubtsova G.A.,Russian Academy of Sciences | Shitova M.V.,Russian Academy of Sciences | And 9 more authors.
Environmental Biology of Fishes | Year: 2012

A harvested stock of chum salmon homing to Kurilskiy Bay, Iturup Island, consists of two genetically distinct river populations that reproduce in two rivers that drain into the bay and are characterized by limited gene flow. One of these is small and can be regarded as wild, whereas the other is much larger and, until recently, was composed of naturally reproducing components spawning in the river's mainstem and tributaries, with almost no hatchery reproduction during the past two decades. The only human impact on reproduction of the chum salmon stock was regulation of the escapement, with officially accepted limits to avoid 'over-escapement'. Recently the hatchery began to release a large amount of chum salmon juveniles. As confirmed by data on variation in both age composition and microsatellite DNA, first-generation hatchery-origin fish that returned from the first large releases occupied spawning grounds and presumably competed directly with, and potentially displaced wild fish. The most dramatic example is a genetically distinct beach-spawning form of chum salmon that was swamped by much more numerous hatchery-origin fish of the river-spawning form. In order to restore and support naturally reproduced population components, careful estimation of the carrying capacity of natural spawning grounds is necessary with efforts to increase escapement to these habitats. We also recommend concerted efforts to restore and conserve a unique beach-spawning population of chum salmon. We further recommend development of a marking program for direct estimation of straying and evaluation of ecological and genetic impacts of hatchery fish on neighboring wild and natural populations. © 2011 Springer Science+Business Media B.V.

Zhivotovsky L.A.,The Federal Fishery Agency | Tochilina T.G.,The Federal Fishery Agency | Shaikhaev E.G.,Ni Vavilov Institute Of General Genetics | Pogodin V.P.,The Kurilsky Hatchery | And 2 more authors.
Journal of Fish Biology | Year: 2016

Mature hybrids between chum salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha, which were identified by an intermediate colour pattern, were caught at the Kurilsky Hatchery, Iturup Island, Russia. Most of them were female and 3 years old (a partial freshwater year and 2 marine years), which is intermediate between the ages of maturity of the parental species. The hybrids exceed both parental species in the rate of growth, are large in size and robust and might successfully compete for mating in the wild or be chosen for artificial reproduction. The ratio of the scale length over width, R, is oblate (R < 1), whereas scales of the parental species are prolate (R > 1). From scale analyses, the c.v. in body size of hybrid females at the second marine year is twice that of O. keta, which suggests developmental instability in the hybrid. A dynamic model predicted that continuing hybridization at a low rate does not produce a substantial hybrid load due to selection against advanced-generation hybrids and backcrosses. A high hybridization rate, however, may be an additional risk for genetic management and should be taken into account in programmes of artificial reproduction of Pacific salmon Oncorhynchus spp., although such hybrids might have commercial use in confined production systems. © 2016 The Fisheries Society of the British Isles

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